The nutrients are.
Beyond simply labeling something “healthy” or “unhealthy,” the NOVA classification system in human nutrition offers a perspective based on the extent and purpose of food processing. Often people try to attribute this same system to the pet food industry, and make sweeping claims that less processed = better.
However, does this classification system actually make sense for pet food? And can we draw any conclusions about the health of animals being fed a so-called “ultra-processed diet”?
So, what is the NOVA Classification System?
The NOVA system divides foods into four groups:
adapted from Monteiro et al. (2018)
1. Minimally Processed Foods: These are the closest to their natural state, undergoing minimal changes like cleaning, drying, or freezing. Think fruits, vegetables, whole grains, legumes, nuts, seeds, meat, fish, eggs, and milk.
2. Processed Culinary Ingredients: These are derived from Group 1 foods through simple processes. Examples include vegetable oils, butter, cheese, honey, sugar, and salt.
3. Processed Foods: These are made from Group 1 and/or Group 2 ingredients with added salt, sugar, or oils. Canned fruits and vegetables, bread, cheese, and processed meats fall into this category.
4. Ultra-Processed Foods: This group includes formulated foods made from ingredients like refined oils, starches, added sugars, and artificial flavors. Fast food, packaged snacks and sugary drinks fall under this category.
But is it helpful?
The use of the NOVA classification has a few major drawbacks however, that limit how useful it is when we are discussing nutrition.
1. Oversimplification: It oversimplifies complex food systems. For example, some minimally processed foods may be nutrient-poor, while some ultra-processed foods can be fortified and offer nutritional value.
2. Subjectivity: Classifying foods can be subjective, with varying interpretations of “processed” and “ultra-processed”
3. Limited Consideration of Cultural and Dietary Diversity: The system may not fully account for the diverse ways people around the world prepare and consume food, and risks the demonization of certain foods or food groups that are necessary for the survival of individuals. For example, Total Parenteral Nutrition (TPN) that some individuals rely upon to meet their nutritional needs would be considered “ultra-processed” despite being nutrient dense.
4. Potential for Misinterpretation: Focusing solely on processing level can overshadow the importance of overall dietary quality and individual nutritional needs, taking the focus off the nutritional value of products.
Braesco, et al. (2022) explored the NOVA classification system to see how functional it is when assessing a foodstuff. They unfortunately found among nutrition specialists that grouping foods under this system was inconsistent and too subjective to be of any real value. They also noted that products assigned to NOVA4 (ultra-processed) varied greatly in nutritional value and therefore the consumer’s selection of NOVA4 foods had a greater influence on diet quality – not purely the selection of a NOVA4 food;
Here, we found that foods most commonly assigned to NOVA4 (i.e., NOVA4maj foods) could vary substantially in their nutrient profiles, possibly in relation to the large heterogeneity of their composition. Thus, diet quality is more likely to be determined by specific consumer choices from among NOVA4 foods than by a food’s assignment to NOVA4 in and of itself. Confusing messages may arise from front-of pack labeling, such as when products with a NOVA4 label, signifying their ultra-processed nature, would also bear a label conveying their good nutritional quality.
How does this relate to pet food?
The process of manufacturing a kibble product utilises ingredients such as starches and fibres, purified omega oils and animal fats, and protein sources that are typically in a dehydrated or ground form (meal) when entering the extruder. In addition, any nutritional gaps in the formulation are accounted for with the addition of vitamin/mineral packs.
At first glance, you’d slap it with the label ultra-processed and put it under NOVA4. Unfortunately this doesn’t tell us anything about the nutritional profile of the product, like mentioned above in Braesco’s study. We cannot tell anything about the nutritional profile of a product simply by it’s NOVA classification alone.
A complete and balanced kibble diet contains – by definition – all the nutrients necessary in the correct ratios to sustain life for the species and lifestage it’s intended for. Regardless of its “processing” level, this is the minimum standard a commercial product must meet.
By contrast, a home cooked diet would be considered minimally processed, but 95% of homecooked recipes online and in textbooks are deficient in one or more nutrients. So therefore it might be classified in NOVA1 but would be seriously lacking in nutritional value, potentially more hazardous to health than a NOVA4 “kibble”.
Conversely, a raw diet that would be considered un-processed or minimally processed has similar challenges with nutritional adequacy but also the added risk of food borne illness – the act of processing the product makes it safer by killing pathogens. Raw pet food, time and time again, has been shown to be a risk to both pet health and human health, with the most recent outbreaks of H5N1 Avian Influenza claiming the lives of two cats and sickening several others.
What is healthy?
The definition of a healthy diet is a diet that maintains or improves overall health. A healthy diet provides the body with essential nutrition: fluids, macronutrients such as protein, fats and carbohydrates, micronutrients such as vitamins and minerals, adequate fibre and energy.
In the context of pet food, this would mean the diet must provide at least all the essential nutrients in the correct ratios necessary for the particular lifestage and species, without causing any detriment to the patient’s overall health. This is what we call a complete and balanced diet that we described above.
And by this definition – maintaining or improving health – this would exclude most “unprocessed foods” that contain harmful pathogens or are nutritionally inadequate, and include most “ultra-processed foods” in the context of pet nutrition.
So can we use NOVA in pet nutrition?
As we discussed above, just because something is less processed, does not necessarily mean it is automatically healthier. So while you can of course use the NOVA system, why would you really want or need to?
Processing serves a purpose, whether that is to improve the safety of food (to remove pathogens), to improve the palatability or digestibility of a diet that is medically necessary for patients, or to improve the nutritional profile and bioavailability of certain nutrients in foods which will maintain or improve the consumer’s health.
While you can of course classify any food based on its processing level, this tells us very little about how “healthy” or “unhealthy” it is. This classification system is unfortunately highly subjective and not designed for pet food, so we can’t really use it to draw valuable conclusions – even human dieticians are beginning to move away from the NOVA system.
The processing levels of a diet isn’t the problem – it’s the nutrient levels. We should always bring our minds back to what our nutritional goals are for our pets, and understand where to extract that information and how that fits into the wider context of our pet’s health, rather than simply classing foods based on their level of processing and ignoring their benefits or drawbacks in the wider context of the patient’s dietary needs and history.
References
Ultra-processed Foods, Weight Gain, and Co-morbidity Risk – Scientific Figure on ResearchGate. Available from: https://www.researchgate.net/figure/Spectrum-of-processing-of-foods-based-on-the-NOVA-classification-The-figure-provides_fig1_355481122 [accessed 5 Jan 2025]
Braesco, V., Souchon, I., Sauvant, P. et al. Ultra-processed foods: how functional is the NOVA system?. Eur J Clin Nutr 76, 1245–1253 (2022). https://doi.org/10.1038/s41430-022-01099-
Stockman J, Fascetti AJ, Kass PH, Larsen JA. Evaluation of recipes of home-prepared maintenance diets for dogs [published correction appears in J Am Vet Med Assoc. 2014 Jul 15;245(2):177]. J Am Vet Med Assoc. 2013;242(11):1500-1505. doi:10.2460/javma.242.11.1500
Vecchiato CG, Schwaiger K, Biagi G, Dobenecker B. From Nutritional Adequacy to Hygiene Quality: A Detailed Assessment of Commercial Raw Pet-Food for Dogs and Cats. Animals. 2022; 12(18):2395. https://doi.org/10.3390/ani12182395
Kang YM, Heo GB, An SH, et al. Highly Pathogenic Avian Influenza A(H5N1) Virus Infection in Cats, South Korea, 2023. Emerg Infect Dis. 2024;30(12):2510-2520. doi:10.3201/eid3012.240154
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